Top end sugestion, valve springs and rpms

Message

peterock · #21 Post by **peterock** » Tue May 08, 2007 4:45 am

Steve,

We should be set this time around. Will know for sure tomorrow night as I should have my fuel pump then. Just turning over by hand has a lot more compression then the other day.

Posted pics on cannondalecentral.com to many to repost here.

peterock · #22 Post by **peterock** » Wed May 16, 2007 4:36 am

Well we did some more work and have appeared to found our issue. Decomps need to be ground down about .028 in . Doesn't seem like a lot but that is the difference between a 220 shim and a 290 shim. The difference is a result of 25psi compression or 85-90psi compression.

Happyboy · #23 Post by **Happyboy** » Wed May 16, 2007 5:51 pm

I don't follow. Why would the decomp have to be grounded down? Did you chance the base circle?

peterock · #24 Post by **peterock** » Wed May 16, 2007 9:14 pm

Cams were undercut. What this will allow us to do is to take a slightly worn cam and reuse it without welding it and plus change the profile. Cams we are testing had excive wear so they had to be welded anyway.

So simple answer is yes, the base circle is smaller. Add larger shims to compensate but allows the cam profile to be changed. profile now is basically 10 degrees more lift and 10 degress more duration.

peterock · #25 Post by **peterock** » Thu May 17, 2007 2:59 pm

Steve put some more hours in closing up the motor and putting it back in the frame.

Fired it up this morning. now for durability testing and hopefully dyno time.

cannondale27 · #26 Post by **cannondale27** » Thu May 17, 2007 4:52 pm

Having that one fire up was sure a relief.Lost count on how many times we had topend apart chasing this.Pete is a real gogetter and hard worker for sure.I am sure he understands the importance of long term testing.The decomp mod was not something I liked to do.But who knows it may work out just fine with the much lower spring pressures being tried here.Here are some more pics:

ATK wort removal.Still rears its ugly head.ATK we dont cut corners you should be fixing all the cranks that were welded like this.May have even led to your wristpin failures.

cannondale27 · #27 Post by **cannondale27** » Thu May 17, 2007 5:04 pm

Decomp pin mod.Taking .028 off is easy but really half moon shape should be held.That is impossible since by time it is half moon shaped with .028 taken off contact point I think it would be way too small and weak.Just took a good guess as to how much to round it off.Got lucky so far.Hope it doesnt mar the bucket or break off but who knows.Could easily happen.Sorry about pic quality.

Happyboy · #28 Post by **Happyboy** » Thu May 17, 2007 5:50 pm

Eh, I would be worried about that decomp pin now. Maybe it won't be a problem but strength and a smooth transition is a must with that piece.

peterock · #29 Post by **peterock** » Thu May 17, 2007 6:23 pm

We shall find out. Keep in mind we are using lighter valve springs so there should be less force/pressure however you want to say it on all the components.

Received notice today that the TI ported head should ship out today.

So probably be tearing it back down shortly again and we'll be able to check all the components for wear.

cannondale27 · #30 Post by **cannondale27** » Thu May 17, 2007 6:29 pm

Strength could be issue but transition wont.Stock Half moon part is what would be hitting first.I didnt take any off the dia except where it touches bucket.Looks like I did because I polished the whole thing.The corner that is there never touches bucket.Unless valve floats